The goal of the PI's research is to understand the development of simple cognitive function in neonates. Throughout an organism's life span, there are periods of time when learning is potentiated. This facilitated learning is presumably due to changes in an underlying neural structure. The goal of the present proposal is to document the changing characteristics of a specific brain area and its functional significance in potentiated learning in infancy. The PI's previous research has characterized a developmental epoch in infant rats in which the ability of pups to learn is greatly enhanced. However, this potentiated learning is not expressed through more rapid learning, attenuated extinction or longer retention. Instead, the significant factor for this potentiated learning appears to be based on the broad spectrum of stimuli which can function as reward for infants. For example, pairing an odor with either tactile stimulation, tailpinch or intra-oral milk infusions results in a subsequent odor preference. This "sensitive period" for learning takes place during the first two weeks of the rat pup's life. Through her previous work, the PI has demonstrated that norepinephrine is critical for learning during this "sensitive period". Blocking norepinephrine prevents olfactory learning. Furthermore, pairing an odor with norepinephrine is sufficient to produce an odor preference. Additionally, manipulation of the noradrenergic locus coeruleus also influences learning: stimulating the locus coeruleus during an odor presentation is sufficient to produce an odor preference and lesioning this brain area prevents learning. Work from other laboratories has demonstrated that the noradrenergic locus coeruleus has unique characteristics during the olfactory learning "sensitive period" which greatly increases its response to stimulation. Indeed, the locus coeruleus is activated by the same unique broad spectrum of stimuli which can function as reward in infants. For example, in contrast to the adult locus coeruleus, the neonatal locus coeruleus exhibits a robust response to tactile stimulation and tailpinch. Qualitative and quantitative properties of receptors, as well as biophysical properties of locus coeruleus neurons appear to be responsible for the unique response characteristics of the neonatal locus coeruleus. The specific goal of the present proposal is to explore the relationship between the "sensitive period" for learning and the immature locus coeruleus. To this end, the unique characteristics of the locus coeruleus will be manipulated to assess its effects during learning. Additionally, the locus coeruleus's role in learning in other sensory systems will be assessed to determine whether the locus coeruleus has a more general role in neonatal learning.